HÀ NỘI — The water quality in Hà Nội’s lakes, including 86 in the inner city and 44 on the outskirts, earmarked for renovation has improved markedly after months of dredging and cleaning, experts have announced.

Lakes such as Ngọc Khánh, Kim Liên, Ba Mẫu and Thiền Quang were once severely contaminated and needed urgent cleaning to protect their bio-systems, safety levels and the surrounding areas.

"I’ve seen a big improvement. The water in the lake [Ngọc Khánh Lake] is cleaner and less smelly," said Vũ Khắc Hòa, a resident of Hà Nội’s Ba Đình District, who lives near Ngọc Khánh Lake.

The surrounding area had also been beautified, he said.

“The investor has separated the water drainage system so the waste water from residential areas no longer flows into the lake,” Văn Đình Hùng, another resident told Vietnam Television.

Bùi Ngọc Uyên, from Hà Nội Sewage and Drainage Company, which is responsible for maintaining Hà Nội’s lakes, said over the past year the company has used chemical products together with a number of measures like the installation of aquatic rafts with a view to increase oxygen and the self-cleaning ability of the lakes.

The main task for Hà Nội lakes is to regulate drainage, drought and environmental landscapes and they have met these criteria, experts say.

According to the Centre for Environment and Community Research (CECR) report released in 2015, the number of lakes in Hà Nội reduced to 112 from 122 between 2010 and 2015. The water surface reduced by 72,000 sq.m compared with 2010.

Data from the CECR analysis showed that a lot of lakes, which were once beautiful spots for the city’s residents to visit and enjoy, were seriously deteriorating due to rising levels of pollution.

Test on water samples taken at these lakes revealed that lakes contained an excessive amount of pollution, compared to national standards.

To improve the water environment at lakes, the municipal People’s Committee had assigned the Department of Natural Resources and Environment to research and implement the testing and treatment of water pollution in rivers and lakes in the city.

The experiment was conducted in 12 lakes including Ngọc Khánh, Xã Đàn, Hai Bà Trưng, Kim Liên, Ngọc Hà, Đền Lừ, Văn Quán, Giảng Võ. In addition, the Department handled the pollution of water in Hồ Tây (near the Water Park) and Mỹ Đình ditch.

Algae are planted during a pilot programme on Thành Công Lake in Hà Nội as a way to absorb the pollutants and purify the lake’s water. — VNA/VNS Photo Bùi Tường

In 2016, the City People’s Committee has directed Hà Nội Sewage and Drainage company to implement the treatment of Redoxy-3C technology for 83 lakes in the city to enhance the water quality.

After the product was proved effective during trials in Hố Mẻ, Ba Mẫu and Giáp Bát Lake, Redoxy-3C has been applied to other lakes in the city including Hoàn Kiếm Lake (Returned Sword Lake).

Covering an area of around 12 hectares, the lake is located in the historical centre of the city. Not only important historically, Hoàn Kiếm Lake has a beautiful landscape, and is considered a scenic, relaxing escape from the chaos of the Old Quarter.

However, the lake is severely polluted and has lost the ability to revive itself. Its water quality is getting worse by the day, its pH level is high, and the amount of suspended deposits is higher than the permissible limit at all five monitoring locations, according to Hà Nội Sewage and Drainage Company.

The lake also has high organic contamination, with the indices for both biochemical oxygen demand (BOD) and chemical oxygen demand (COD) two times over the limit.

The lake water has lost its distinctive dark green colour in several spots, and there is a one-metre layer of mud at the bottom of the lake, causing pollution and reducing the water level by 0.5 to 0.8m.

By the end of last year, the company was assigned to dredge and clean Hoàn Kiếm Lake.

After over one month of cleaning, the original colour of water in the lake has returned and there is no longer a bad smell.

Phạm Tùng Lâm, head of the Management Board of Hoàn Kiếm Lake, said the polluted mud layer disappeared when the dredging process had finished.

“It would be a good opportunity for aqua-culture and creatures to develop in the lake,” he said adding that as a matter of fact, a tortoise had been seen laying eggs near Ngọc Sơn temple. — VNS